In a system structure of a conventional electric vehicle DC/DC converter, an output voltage reference that is generated from a microcomputer is compared with an output voltage detection value and a conduction ratio of a switching element is controlled such that an output voltage coincides with the voltage reference (for example, refer to Non-patent Document 1).
According to domestic output voltage specifications disclosed in Non-patent Document 1, a variation range of ±10% is allowed. In general, a voltage variation range of only about ±1% is allowed according to overseas specifications, which requires a high precision as compared with the case of the domestic specifications. Therefore, in order to realize a high-precision converter device that satisfies the overseas specification, a countermeasure is required to be taken against an instant voltage variation, for example, by increasing a switching frequency to speed up a control response, by increasing the capacitance of a smoothing capacitor, or by adding an over-voltage prevention hardware.
Non-patent Document 1: Eiji Sawano and other 6 persons, “High frequency link system DC/DC converter device using IGBT”, Institute of Electrical Engineers of Japan of 1995, National convention, lecture collected papers, 1995